1. Field of the Disclosure
The present invention relates to a level shift circuit with improved dv/dt sensing and noise blocking.
2. Related Art
Level shift of high voltage signals (up to several hundred volts) is an essential feature of most power systems. Level shifting allows for isolation between low voltage control signals and a relatively high voltage switching power output, for example. High voltage level shifting is typically accomplished using high voltage isolation technology. However, this technology typically has long propagation delays and a relatively low operating speed. As new applications and system architectures are developed, operational speed requirements are often in the range of Megahertz, thus the delays present in the conventional technology are not acceptable.
More specifically, traditional high voltage level shift schemes have several disadvantages in both cost and performance. First, the Hall effect sensors and optical isolation devices typically used are bulky and slow. Further, these elements are also difficult to integrate onto a chip. As is mentioned above, present technology is also typically subject to low frequency operation in light of the propagation delays noted above. In addition, these systems are also subject to limited pulse width linearity and high power dissipation. Further, some of these systems such as, for example, the cross-coupled high speed level shift circuit described in U.S. Pat. No. 7,212,033 are sensitive to fabrication mismatches.
Accordingly, it would be beneficial to provide a level shift circuit that avoids the problems discussed above.